Management of Microscopic Algae in the Western Basin of Monponsett Pond Phosphorus Inactivation Program

Transcription

1 Management of Microscopic Algae in the Western Basin of Monponsett Pond Phosphorus Inactivation Program William E. Stevenson, President Joy Trahan Liptak, Biologist Brittany Laginhas, Biologist

2 Pond Characteristics Western Basin 528 acres Eastern Basin 282 acres 246 acres Avg. Depth: 7 ft. Max. Depth: 13 ft. Approximately 6mi 2 watershed, heavily developed with residential homes (d) list category 5 water body for nutrients, noxious aquatic plants, turbidity, and exotic species (Fanwort) Extensive algae blooms resulting in closure of the lake (swimming and boating) for much of the summer seasons of 2010 and (d) list category 4c water body for presence of exotic species (Variable Milfoil and Fanwort), 2007 TMDL for Hg Periodic algae blooms Confirmed presence of three state listed species of special concern: Tidewater Mucket (Leptodea ochracea), Eastern Pondmussel (Ligumia nasuta), and Umber Shadowdragon (Neurocordulia obsolete)

3 The Problem Harmful Algae Blooms (HABs) Decrease in water clarity Unpleasant odors Drinking water quality decreases Extensive beach closures skin and eye irritation gastrointestinal symptoms asthma like symptoms toxins may be produced (hepatotoxins, neurotoxins) West East

4 Algae Natural components of healthy ecosystems Ideal conditions produce blooms! nutrients ( )! warm weather! light availability! low turbulence

5 Solutions 1. Watershed Management Identify nutrient sources Fertilizers (residential & agricultural) Sewage (old septics) Stormwater Conduct remediation efforts

6 Solutions 2. In Lake Management: Copper Treatment Direct treatment of algae Only affects algae present during treatment Reactionary treatment required at specific time (algae dependent) If algae counts are too high, treatment not possible (could result in fish/mussel kills) Multiple treatments per year likely

7 Solutions 3. In Lake Management: Phosphorus Inactivation Aluminum sulfate, a.k.a. alum Binds to phosphorus, precipitating it to the bottom Byproducts can lower ph in poorly buffered water bodies Buffering agent (sodium aluminate) added with alum to maintain ph Addition of alum Coagulation Flocculation Sedimentation

8 Monponsett s Alum Treatment Goals of the 2013 Treatment Reduce Phosphorus in the water column Evaluate the effects of low dose alum on: In water Phosphorus Algae production State listed species

9 Monponsett s Alum Treatment Permits DEP/Natural Heritage & Endangered Species Program (NHESP) Management of State listed species habitat Town Orders of Conditions (Hanson & Halifax) EPA NPDES Permit MA DEP License to Apply

10 Monponsett s Alum Treatment Treatment Design Areas >4ft. to reduce effects of wind/waves on floc 3 ppm Buffered treatment: Aluminum sulfate + Sodium aluminate Treatment area broken into 3 sections, 2.77 acre sectors Multi day operation (~1 week)

11 Monponsett s Alum Treatment Monitoring Program Design Monitoring Component Large scale jar test Water quality Measurement of flocculation Monitoring of state listed species Sediment cores Timing in relation to treatment 2 weeks prior Before, during, and after months and years following During Before, during, and after One and five years following Before and after One month, one and five years following Location(s) Treatment staging area 10 established locations; multiple locations during treatment 1 visual recording; 6 measurement locations 5 paired plots 3 established locations Goal Verify that ph in the treatment area will remain within the target range of 6.5 and 7.5 Evaluate short and long term effects on water quality Assess the amount of floc accumulated on the sediments Evaluate short and long term effects on these species identified by NHESP as potentially susceptible to the treatment Assess changes in AL and sediment P

12 Monponsett s Alum Treatment 2013 Schedule

13 Monponsett s Alum Treatment 2013 Schedule! Jar Testing! Monitoring Baseline Assessments! State listed species! Sediment! Water quality May 2013 June! Alum treatment! Monitoring! Water quality! State listed species! Monitoring! Water quality! Sediment July May 2014! Monitoring! State listed species! Sediment! Water quality Following final monitoring and report, NHESP/DEP will determine if additional treatment(s) are possible

14 Things to Remember Treatments are not a magic wand Further review will be required Control of nutrient source(s) is the best option for long term lake management!!

15 Questions?